fixed yaml config error

RickieL · RickieL · commit 6c4230940dea · 2016-04-05T09:36:11.000+08:00
fixed the error of yaml config. 
error info is "Unrecognized option "charset" under "doctrine"
diff --git a/book/doctrine.rst b/book/doctrine.rst
@@ -150,8 +150,8 @@ can automatically generate an empty ``test_project`` database for you:
 
             # app/config/config.yml
             doctrine:
-                charset: utf8mb4
                 dbal:
+                    charset: utf8mb4
                     default_table_options:
                         charset: utf8mb4
                         collate: utf8mb4_unicode_ci
